Method for transporting a weft thread through a weaving shed and a loom for performing said method

ABSTRACT

A method and apparatus for transporting a weft thread through a weaving shed, by discharging a plurality of aligned jets of transport fluid at points spaced along the shed, the jets being energized successively, in time with the advancement of the leading end of the weft thread, to cause the jets to entrain the leading end of the weft thread progressively and thereby draw the weft thread through the shed.

The invention relates to a method for inserting a weft thread into aweaving shed using a plurality of jet nozzles for supplying a transportfluid arranged spaced along the width of the shed. The invention alsorelates to a loom of the type in which the wefts are transported throughthe shed by means of a plurality of jet nozzles for supplying transportfluid arranged spaced along the width of the shed.

Various weaving defects have been found to result in looms of the saidtype from the conduct of the wefts during their transport through theshed. Among them are weaving defects resulting from the tendency of thewefts to lodge themselves in the boundary layer surrounding each jetcone issued by each separate jet nozzle. Further by all kinds of causese.g. by cushion building of the transport fluid in the shed, deviationsof the wefts may occur whereby the above mentioned weaving defects maybe originated.

SUMMARY OF THE INVENTION

The present invention aims at contributing to avoiding the abovementioned weaving defects and the invention is directed to animprovement in the energy transmission from the transport fluid to thethread moving through the shed.

Extensive experiments have shown that the energy transmission from aconical or differently shaped jet is greatest during the period in whichthe jet cone is adjusting itself and therefore during a period in whichthe forming of the boundary layer is still in full swing. Where thenature of the jet cone varies less in function of time the energytransmission and therefore the force applied to the thread becomessmaller.

Using this principle the invention proposes to energize the jet nozzlessuccessively or in successive groups in time with the advancement of theleading end of a weft thread through the shed. It appears that theenergy transmission is improved thereby in such a way that the increasedforce acting upon front thread end which force under the improvedcircumstances acts continuously on said thread end is already able byitself to cause the weft to be transported through the shed at thedesired high velocity. Therefore according to a further feature of theinvention the supply of the transport fluid to each jet nozzle or toeach group of jet nozzles respectively is interrupted or at leastdecreased as soon as the weft has arrived in the influence area of thenext jet nozzle or the next group of jet nozzles respectively. Not onlyis the total consumption of transport fluid by the different jet nozzlesthus reduced to a fraction of the consumption as heretofore present inlooms of the type mentioned, but the weft also tends to proceedaccording to a more tautly extending path than if the jet nozzles orgroups of jet nozzles already passed by the front end of the threadwould continue to inject fluid and thereby would continue to act onintermediately situated points of the thread. Further said interruptionof the supply to the jet nozzles opens the possibility of applyinghigher pressures, at least in the jet nozzles arranged at the entranceof the shed, than heretofore was acceptable in view of the danger ofsaturation of the shed and the possibility of cushion building.

Preferably the supply of the transport fluid to a jet nozzle or to agroup of jet nozzles is opened before the supply of the preceding jetnozzle or the preceding group of jet nozzles is terminated or reduced inorder to obtain a certain overlap by which any variations in the pointof time in which the thread is launched by the launching device of theloom are compensated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a weaving shed with a plurality ofschematically shown jet nozzles therein;

FIG. 2 shows a diagram in which the air consumption during a weavingcycle is registered and

FIG. 3 shows a simplified scheme for controlling the supply to thesuccessive jet nozzles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows schematically an arrangement known per se of a plurality ofjet nozzles 1-6 which at least with their outflow openings extend intothe shed outlined by the upper warp sheet 7, the under warp sheet 8 andthe reed 9. The jet nozzles 1-6 serve to transport the weft 11 launchedat 10 in the direction of the arrow 1 through the shed shown whereafterthe reed 9 is moved in the direction of the arrow 11 in order to beat upinto the cloth the weft inserted in this way.

As shown in FIG. 1, the jet nozzles 1-6 are spaced from one another andare aligned and arranged to discharge a transport fluid in the samedirection to transport the weft thread 11. Each of the jet nozzles 1-6may be constructed and mounted in a conventional manner, for example asshown in U.S. Pat. No. 3,465,791. For the transport of the weft 11through the shed first the supply of the transport fluid, e.g. air, tothe first jet nozzle 1 is opened, which jet nozzle thereby injects aconical jet of the transport fluid in the transport direction into theshed which jet takes along the weft 11 from the point 10 in its path inthe direction of the next jet nozzle 2. It has been established that theweft 11 then lodges or "nestles" itself in the boundary layer formingaround the conical core of the jet. Now the supply of the transportfluid to the jet nozzle 1 is continued up to a point in the weavingcycle just beyond the point at which the supply of the transport fluidto the second jet nozzle 2 is opened. The weft 11 is thereby taken overby the jet issuing from the jet nozzle 2 and taken along by the boundarylayer forming around said jet in the direction of the third jet nozzle3. The energization of the jet nozzle 2 is continued for a short timeinterval after the supply of the transport fluid to the third jet nozzle3 is opened in order to thereby assure that the weft 11 is withcertainty taken over by the jet issuing from the third jet nozzle 3. Thejet issuing from the first jet nozzle 1 has been interrupted at thatmoment for a "long" time already.

FIG. 1 shows an instantaneous picture of the weft 11 during itstransport through the shed. Especially this instantaneous picturerelates to a point of time at which only the third jet nozzle 3 isoperative and the front end of the weft 11 is moving in the direction ofthe jet nozzle 4 carried by the boundary layer around the conical jetissuing from the jet nozzle 3. At that point of time the previouslyactuated jet nozzles 1 and 2 have already been switched off, whereas thesupply of transport fluid to the jet nozzles 4, 5 and 6 situated furtherin the weft direction has still to take place. The weft 11 extends fromthe launching point 10 to the origin of the transport jet issuing fromthe jet nozzle 3 at the considered point of time, according to asubstantially straight line and extends from the said third jet originaccording to a generatrix of the jet cone. Instead of the said straightcourse of the weft between the point 10 and the jet nozzle 3 a moreserrated or sawtoothed course of the weft would be obtained, if thenozzles 1 and 2 would still be operating at the considered moment.

With the method according to the invention the weft 11 will thereforemove along a more tautly extending path through the shed and thereforethe possibility of contact with the upper warp sheet 7, the under warpsheet 8 or the reed 9 will be very small whereby the possibility isobtained to reduce the shed height correspondingly.

It may be seen from the diagram of FIG. 2 what the air consumption iswhen applying the method according to the invention compared with theair consumption with the method applied heretofore. On the abscissa 220°of a weaving cycle of 360° have been drafted. In the first half of theweaving cycle from 0°-180° the transport of the thread 11 from thelaunching point 10 to the opposite side of the shed takes place, whereasin the second half of the weaving cycle, from 180°-360°, the reed 9beats the inserted thread up into the cloth and returns to its startingposition according to the drawing. FIG. 2 shows that the energizing ofthe jet nozzle 1 starts at 0° and ends at 33°, whereas the energizing ofthe second jet nozzle 2 starts at 30° and ends at 63° and so on. In theembodiment shown an overlap of 3° occurs between each two successivetransport jets. The last jet nozzle 6 stays energized during 40° in thesecond half of the weaving cycle in order to keep the inserted weft tautduring the beat up movement of the reed. The sum of the hatched areas inFIG. 2 is a measure for the air consumption during the weaving cycle.This air consumption has to be compared with the air consumption in amethod in which all jet nozzles are supplied at the same time and duringan equally long interval, which last mentioned air consumption may bereproduced by the area of the rectangle limited by the abscissa, theordinate and the lines 13 and 14.

For the control of the supply of transport fluid to the successive jetnozzles 1-6 use may be made of separate valves inserted in the supplylines to the various jet nozzles which valves may be actuated by cams,mounted in phase-shifted relation on a common control shaft. Anothercontrol mechanism allowing higher weaving velocities is schematicallyshown in FIG. 3. Hereby a single control cam 15 is used which is drivenby the operating mechanism of the loom so that it rotates once for eachstroke of the reed 9. With each rotation of the cam 15, a weft thread 11is launched into the shed as the cam 15 acts to keep open a valve pin 16in a pilot air conduit 17 during a time interval corresponding to thesupply time of the jet nozzle 1, in order to shift a control slide 18against the action of a return spring 19, in a valve which belongs tothe first jet nozzle 1 or to a first group of jet nozzles, to a positionin which the jet nozzle 1 is in communication with a source 20 oftransport fluid under pressure. At the same time the control slide 18forms part of a pilot mechanism which connects the valve which suppliesthe jet nozzle 1 to the valve which supplies the jet nozzle 2. Thispilot mechanism includes a conduit 22 and operates, during the period ofenergization of the jet nozzle 1, to connect the source 20 with acontrol slide 21 belonging to the second jet nozzle 2 or to a secondgroup of jet nozzles. The conduit 22 between the control slide 18 andthe control slide 21 is such that the pressure signal transmitted by theconduit 22 reaches the control slide 21 with a retardation correspondingto the desired time interval between the start of operation of thecontrol slide 18 and the start of operation of the control slide 21. Thecontrol slide 21 will therefore connect the source 20 with the secondjet nozzle 2 or the second group of jet nozzles only at a moment atwhich the first control slide 18 under the influence of the returnspring 19 is about to return to its deenergized closed position. Asindicated in FIG. 3, the control slide for each valve is connected tothe succeeding control slide, to provide pilot mechanism which connectseach succeeding valve to the preceding valve and which causes each valveto open momentarily, after the opening of a preceding valve. In thisway, the mechanism illustrated in FIG. 3 causes each of the valves to beenergized for the proper interval and in the proper sequence as shown inFIG. 2. It is clear that in this way a great many control slides, eachbelonging to a jet nozzle or a group of jet nozzles, may be placed inseries.

It is to be noted that the supply of the transport fluid to the separatejet nozzles during the energization need not be constant, but may e.g.also be pulsating.

I claim:
 1. A method of transporting a weft thread through a weavingshed by discharging .Iadd.only .Iaddend.a .[.plurality.]. .Iadd.singlerow .Iaddend.of aligned jets of transport fluid at points spaced alongthe .Iadd.interior of the .Iaddend.shed, wherein the improvementcomprises the steps of energizing the jets successively, in time withthe advancement of the leading end of the weft thread, to cause the jetsto entrain the leading end of the weft thread progressively and therebydraw the weft thread through the shed.
 2. A method according to claim 1comprising the steps of progressively reducing the amount of fluiddischarged in the jets so that the flow of fluid in each jet is reducedas the leading end of the weft thread approaches a succeeding jet.
 3. Amethod according to claim 2 wherein the reduction in the amount of fluiddischarged in each jet is performed after a succeeding jet has beenenergized.
 4. A method of transporting a weft thread through a weavingshed by discharging .Iadd.only .Iaddend.a .[.plurality.]. .Iadd.singlerow .Iaddend.of aligned jets of transport fluid at points spaced alongthe .Iadd.interior of the .Iaddend.shed, wherein the improvementcomprises the steps of progressively reducing the amount of fluiddischarged in the jets so that the flow of fluid in each jet is reducedas the leading end of the weft thread approaches a succeeding jet. 5.Apparatus for transporting a weft thread through a weaving shed,including .Iadd.only .Iaddend.a .[.plurality.]. .Iadd.single row.Iaddend.of spaced aligned nozzles arranged .Iadd.in the interior of theshed .Iaddend.to discharge a transport fluid in the same direction totransport a weft thread, wherein the improvement comprises mechanismwhich energizes the nozzles successively, in time with the advancementof the leading end of the weft thread, to cause the resulting jets toentrain the leading end of the weft thread progressively and therebydraw the weft thread through the shed.
 6. Apparatus according to claim 5wherein the improvement comprises mechanism which energizes the nozzlessuccessively, in time with the advancement of the leading end of theweft thread, to cause the resulting jets to entrain the leading end ofthe weft thread progressively and thereby draw the weft thread throughthe shed and which progressively reduces the amount of fluid dischargedfrom the nozzles so that the flow of fluid from each nozzle is reducedas the leading end of the weft thread approaches a succeeding nozzle. 7.Apparatus .[.according to claim 6.]. .Iadd.for transporting a weftthread through a weaving shed, including a plurality of spaced alignednozzles arranged to discharge a transport fluid in the same direction totransport a weft thread, wherein the improvement comprises mechanismwhich energizes the nozzles successively, in time with the advancementof the leading end of the weft thread, to cause the resulting jets toentrain the leading end of the weft thread progressively and therebydraw the weft thread through the shed and which progressively reducesthe amount of fluid discharged from the nozzles so that the flow offluid from each nozzle is reduced as the leading end of the weft threadapproaches a succeeding nozzle, and .Iaddend.wherein the mechanism whichenergizes the nozzles comprises a source for supplying a transport fluidunder pressure, a valve which connects each of the nozzles to suchsource, and pilot mechanism which connects each valve after the firstvalve to the valve for a preceding nozzle and which causes each valve toopen momentarily, after the opening of the valve for such precedingnozzle.
 8. Apparatus for transporting a weft thread through a weavingshed, including .Iadd.only .Iaddend.a .[.plurality.]. .Iadd.single row.Iaddend.of spaced aligned nozzles .Iadd.in the interior of the shed.Iaddend.arranged to discharge a transport fluid in the same directionto transport a weft thread, wherein the improvement comprises mechanismwhich progressively reduces the amount of fluid discharged from thenozzles so that the flow of fluid from each nozzle is reduced as theleading end of the weft thread approaches a succeeding nozzle. .Iadd. 9.Apparatus according to claim 6 wherein said nozzles are energized insuccessive groups and wherein a reduction in the amount of fluiddischarged in each group of nozzles is performed after a succeedinggroup of nozzles has been energized..Iaddend. .Iadd.
 10. A method oftransporting a weft thread through a weaving shed by discharging, atpoints spaced along the interior of the shed, the jets of only a singlerow of aligned jets each directing a stream of air in a direction toconvey a weft across the interior of the shed, wherein the improvementcomprises the steps of energizing the jets successively in time with theadvancement of the leading end of the weft thread to cause the jetsprogressively to entrain the leading end of the weft thread and therebydraw the weft thread through the shed and of progressively reducing theamount of air discharged in the jets so that the flow of air in each jetis reduced as the leading end of the weft thread approaches a succeedingjet which has been energized..Iaddend. .Iadd.
 11. A method according toclaim 10 wherein the flow of fluid in a group of jets is reduced as theleading end of the weft thread approaches a succeeding group ofjets..Iaddend. .Iadd.12. A method according to claim 10 wherein the jetsare energized in successive groups and wherein a reduction in the amountof fluid discharged in each group of jets is performed after asucceeding group of jets has been energized..Iaddend.